With the increased demand for radio frequency (RF) systems, there has been a corresponding interest in integrating RF systems on silicon-based integrated circuits instead of using discrete semiconductor components. Examples of RF systems include, for example, automotive radar and high frequency communication systems. By using silicon integration, large volumes of these RF systems can be manufactured at lower costs than discrete component-based systems.
One type of circuit component frequently employed in RF systems is mixer. Mixers generally mix a signal having a first frequency with a signal having a second frequency, resulting in a signal having a third frequency, where the third frequency may be, e.g., a frequency equal to a difference between the first frequency and the second frequency. For example, mixers are used in frequency downconverters. For such downconverters, an incoming RF signal is mixed with a local oscillator (LO) signal resulting in an intermediate frequency (IF) signal which may then be further processed.
During semiconductor manufacturing, RF circuits or devices, such as mixers, are often tested after being fabricated. Conventional methods for testing RF devices, however, may be difficult and comparatively expensive. For example, in devices that operate at over 10 GHz, precision test fixtures and expensive test equipment are often needed. These test fixtures and equipment are comparatively time-consuming to operate, calibrate and maintain. For example, RF probes used for testing have a limited lifetime and wear out over time. Physical deformations, such as bent contacts, can affect high frequency matching networks. In addition, corrosion of contacts and connectors can degrade attenuation characteristics of the conventional test setup. As such, even if large volumes of RF integrated circuits can be manufactured, the testing of the RF integrated circuits may become the bottleneck that reduces throughput.